Secondary cerebral edema regulation is of prognostic significance in hypoxic-ischemic encephalopathy (HIE), and aquaporin 4 (AQP4) plays an important role in the pathogenesis of cerebral edema. The traditional Japanese herbal medicine Goreisan relieves brain edema in adults; however, its effect and pharmacological mechanism in children are unknown. We investigated the effects of Goreisan on HIE-associated brain edema and AQP4 expression in a juvenile rat model, established by combined occlusion of middle cerebral and common carotid arteries. Magnetic resonance imaging showed that the lesion areas were significantly smaller in the Goreisan- (2 g/kg) treated group than in the nontreated (saline) group at 24 and 48 h postoperatively. AQP4 mRNA levels in the lesion and nonlesion sides were significantly suppressed in the Goreisan group compared with the nontreated group 36 h postoperatively. Western blotting revealed that levels of AQP4 protein were significantly decreased in the Goreisan group compared with the nontreated group in the lesion side 72 h postoperatively, but not at 12 or 36 h. After 14 days, the Goreisan group had a significantly better survival rate. These findings suggest that Goreisan suppresses brain edema in HIE and improves survival in juvenile rats, possibly via regulation of AQP4 expression and function.
The mechanism of ion extraction from plasma by rf resonance has been studied by one-dimensional particle simulation. The plasma-sheath resonance under the weak magnetic field occurs at the theoretically predicted frequency in the simulation and it has durability. In the rf period at the resonance, the large electric field penetrates into the plasma and the electrons move collectively due to a polarization drift and E×B drift. Two processes are proposed for the ion extraction mechanism. In the first, the rectified electron current in the resonance causes the plasma potential to be higher. Consequently, ions are extracted to a pair of parallel plate electrodes, which sandwich the plasma. In the second, the time-averaged electric field in the plasma region causes ions to accelerate to both electrodes. This means that the restriction of the plasma shielding effect is overcome by the time-averaged electric field.
Sheath thickness dependence on resonance condition during fast ion extraction using a radio frequency resonance methodIn order to raise an ion extraction efficiency from a plasma, a new method using an rf field has been proposed and demonstrated. The resonant frequencies of the rf field were theoretically evaluated to excite the eigenwave of the plasma. The lower frequency of the two plasma-sheath resonances under the magnetic field was selected because it has hardly any dependence on the plasma density when the density is over a critical value. Verification of this method was carried out using Xe discharge plasma ͑electron density, 1ϫ10 16 m Ϫ3 ; electron temperature, 8 eV͒ between the parallel plate electrodes ͑length, 0.5 m͒. The resonance was found at about 10 MHz, which agreed with the theoretical result. The ion current at the resonance was anisotropic and was twice as large as the ion saturated current, which is the limiting value of the conventional electrostatic method.
An ion extraction method using plasma-sheath resonance in a weak magnetic field has been employed to measure the electric field distribution and the time-resolved potential distribution experimentally. The Xe discharge plasma is sandwiched by parallel plate electrodes, which are set parallel to the magnetic field. When resonance occurs at 10 MHz, the electric field perpendicular to the magnetic field has its peak at the midpoint of the electrodes’ length. Therefore, a standing wave seems to be induced in the electrodes. When measuring the time-resolved potential distribution perpendicular to the magnetic field at the midpoint of the electrodes’ length, potential gradients are formed and their directions are reversed in one rf period. It is, therefore, verified that the rf electric field penetrates to the plasma. Moreover, simulation results show that the electric field strength in the resonance increases, but nonlinearly, with the applied voltage.
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